Pump-Probe Electron Beam Timing for Faster SEM Imaging
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Solution Overview
Problem
Pump-probe scanning electron microscopes require multiple scans to detect secondary electrons at all pixel coordinates, leading to increased imaging time and decreased throughput for dimension measurement or defect inspection of semiconductor devices.
Innovation Solution
A charged particle beam device synchronizes the deflection of a pulsed charged particle beam, pulsed light irradiation, and detection timing to reduce the number of scans required, using image restoration techniques to fill in missing pixel data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple scans are performed to detect secondary electrons at all pixel coordinates in a pump-probe scanning electron microscope, then detection completeness is improved, but imaging time increases and throughput decreases
Solution Approach 1:
The patent applies preliminary action by performing a first scan to acquire detection signals at selected pixel coordinates before performing a second scan to acquire signals at remaining pixel coordinates. This preliminary acquisition of partial data allows the system to reconstruct complete images through image restoration techniques, thereby reducing the need for multiple complete scans and improving throughput while maintaining detection completeness.
Solution Approach 2:
The patent segments the scanning process into multiple passes, where each pass acquires data at specific pixel coordinates. Instead of requiring all pixels to be scanned simultaneously or in complete passes, the segmentation allows flexible data collection that can be reconstructed through image restoration, thus resolving the contradiction between complete detection and reduced imaging time.
2Measurement precision
If the electron beam scans the sample multiple times to acquire signals at all pixel coordinates, then image quality is improved, but the imaging time is significantly increased
Solution Approach 1:
The patent applies partial action by acquiring detection signals at only selected pixel coordinates during the first scan rather than scanning all pixels. This partial scanning approach, combined with image restoration techniques, produces sufficient image quality for analysis while dramatically reducing the total scanning time required compared to conventional methods that scan all pixels multiple times.
Solution Approach 2:
The patent uses image restoration to create a complete image representation from partial scan data. The restoration process generates pixel values for coordinates where no direct measurement was taken, effectively creating a copy or reconstruction of the complete image from incomplete data, thus maintaining image quality while reducing scan time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The imaging time is significantly reduced, enhancing throughput by minimizing the number of scans needed while maintaining image quality.
Implementation Method 1
pump light for changing a state such as a charged state, an electron state, and a temperature of a sample is applied
Implementation Method 2
probe electrons for forming a scan image are applied with a delay time TDelay with respect to the pump light
Implementation Method 3
detection sampling is performed according to an irradiation timing of the probe electrons
Data Source
AI summary
A charged particle optical system scans a sample with a pulsed charged particle beam and detects secondary charged particles; and a scan image is formed. Control is carried out so that a deflection signal for deflecting the charged particle beam in a first direction, a first timing for pulsed irradiation, a second timing for pulsed irradiation, and a third timing for detection of the secondary charged particles are synchronized. When the deflection amount of the charged particle beam in the time period of the first timing corresponds to the coordinates of n pixels in the scan image, the same line is scanned m times (m<n) while shifting the first timing with respect to the deflection signal so that a location irradiated with the charged particle beam by each scanning has different pixel coordinates. The pixel values at pixel coordinates where a signal is defective are restored.